A conventional mobile information terminal apparatus has a display unit in respective housings that are foldably coupled to one another and that when unfolded, provide a screen of a large display size (see, e.g., Japanese Laid-Open Patent Publication No. 2003-298700). Further, in the housing of a main display unit of a mobile telephone, two sub-display units are accommodated that are adapted to be pulled out from the housing (see, e.g., Japanese Laid-Open Patent Publication No. 2007-124025). Another conventional mobile communication terminal has a display unit in respective housings that are vertically stacked on one another and that when unfolded, causes the display units to be flatly arranged side by side (see, e.g., Japanese Laid-Open Patent Publication No. 2009-71588). Still further, a displaying apparatus has two display units coupled to one another to enable one display unit to be stacked on the display surface of the other display unit and to move around the other display unit to remain on the back thereof (see, e.g., Japanese Laid-Open Patent Publication No. 2009-109943).
In addition to the foldable electronic devices, sliding-type electronic devices are also present. A sliding-type electronic device transitions between a closed state and an open state consequent to an upper housing thereof sliding on the lower housing thereof. In the closed state, the upper housing overlaps the lower housing and therefore, the upper surface of the lower housing is hidden beneath the upper housing. In the open state, the lower housing and the upper housing are shifted with respect to one another, whereby the upper surface of the lower housing is exposed.
Nonetheless, with a conventional sliding-type electronic device, the upper housing overlaps a portion of the lower housing in the open state and therefore, the area of the exposed portion of the upper surface of the lower housing is smaller than the area of the upper surface of the upper housing. Therefore, a problem arises in that display units of, for example, the same size cannot be disposed in the exposed portion of the upper surface of the lower housing and the upper surface of the upper housing.